1. Technical Field
This invention relates generally to the field of in-flight aircraft de-icing and the like, and more particularly to an electro-expulsive de-icing system and its component parts for aircraft and other applications.
2. Description of Related Art
An “electro-expulsive de-icing system” is also sometimes referred to as an “electro-mechanical expulsive de-icing system.” It uses electrically produced mechanical motion to knock accumulated ice off a flight surface or other object being de-iced. Recall in that regard that ice removal is an important undertaking because, in the case of aircraft, ice can alter aerodynamic characteristics significantly with catastrophic results. A de-icing system alleviates those concerns.
To accomplish aircraft de-icing, a typical electro-expulsive de-icing system includes electro-mechanical transducers called “actuators” that are installed beneath the skin of various aircraft structures (e.g., the leading edges of wings, horizontal and vertical stabilizers, and engine inlets). In response to in-flight ice formation, an onboard electronic control system passes large current pulses through such actuators (e.g., 8,000-ampere, millisecond duration pulses at 30 to 90-second intervals) in order to thereby produce mechanical motion that produces shock waves in the skin of the aircraft structure. The shock waves result in dislodgement of ice that has accumulated on the skin. The actuator impacts the inner surface of the skin, that action produces the shock waves in the skin, and the shock waves knock the accumulated ice off the outer surface of the skin.
Some such existing electro-expulsive de-icing actuators include strips or ribbons of copper or other electrically conductive material that are mounted beneath the aircraft skin in closely-spaced-apart parallel orientation. Electric current flowing as mentioned above causes the strips to accelerate apart from each other in a manner creating ice-removing shock waves. The electrically conductive strips for some actuators take the form of a copper ribbon wrapped in an elongated multi-turn loop (i.e., a multi-turn coil). A copper ribbon measuring, for example, 0.25 inches to 1.50 inches wide and 0.020 inches to 0.040 inches thick, is wrapped in a multilayer, elongated, loop measuring about one to eight feet in length, with the copper ribbon being wound back on itself at the ends of the loop. Molded blocks of polyurethane encapsulate the two opposite folded ends of the loop while a dielectric coating on the copper ribbon prevents shorting between adjacent turns.
Interconnection of the copper ribbon loop to the onboard electronic control system results in electric current pulses flowing in a first direction in a first half of the loop (from a first folded end of the loop to an opposite second folded end), and in an opposite second direction in a second half of the loop (from the second folded end of the loop to the first folded end). As an electric current pulse flows that way, it results in a large force that tends to mutually repel the first and second halves of the loop. That repulsion results in relative movement of the first and second halves away from each other (e.g., by about 0.08″ to 0.50″) in a pulse of mechanical motion that is coupled to the aircraft skin. That mechanical pulse results in the de-icing shock waves.
Although effective in many respects, some existing actuators of the type described above have certain drawbacks that need to be overcome. First, impact of the skin can be less than desired for adequate ice removal. Actuator operation is sometimes less robust than desired. In addition, the ends of the loop tend to experience fatigue failure. For those and other reasons that will become apparent from the following detailed descriptions, a need exists for a better actuator assembly that overcomes the drawbacks discussed above.